The invention relates to a rock drill having a shank and a drill head with a cutting tip on its front end.
Conventional rock drills consist of a drill shank and a drill head, into which a carbide cutting element, which is roof-shaped in side view, is inserted (see FIG. 1 of EP 0 452 255 B1). The cutting element has lips or rake faces which are ground in a wedge shape on either side of the roof-shaped front end and in each case have a top cutting edge. In this case, the cutting edges are arranged so as to be laterally offset from a vertical center plane of symmetry, so that so-called chisel edges are produced (see FIG. 2 of EP 0 452 255 B1).
As a rule, the flanks arranged behind the end cutting edge in the direction of rotation have a flank angle of about 20.degree.-30.degree. compared with a conventional cutting edge angle or rake-face angle of 60.degree., the angles being measured being measured relative to a vertical plane to the longitudinal axis of the drill.
With regard to the design of such cutting tips, reference is additionally made to DE 81 04 116 U1, FIGS. 2 to 4 , and DE 29 12 394 A1, FIG. 1. Some of these drilling tools have secondary cutting tips or corresponding pins which are intended to serve the drilling advance.
The roof-shaped cutting tip made of carbide can pass completely through the drill head over its entire diameter and as a rule forms an additional lateral projecting length for forming the nominal diameter. Provided there are no secondary cutting tips or corresponding pins, the transition region from the drill helix to the drill head is designed as a supporting region for the cutting tip. In this case, to prevent dislodgement, the carbide cutting tip is supported laterally in the drill head by an appropriate, voluminous supporting body, retaining surfaces for the removal of the drillings being formed at the front end as a rule.
A drilling tool having a cemented-carbide insert has been disclosed by EP-A 0353 214, this drilling tool serving to cut rock. In order to produce a better brazed connection between the tool body and the sintered-carbide insert, additional side tips of sintered carbide, which embed the main sintered-carbide insert, are provided. In this case, the sintered-carbide insert is of symmetrical construction relative to its longitudinal center plane, side sections having a different point angle being provided, and these side sections lead to an improved brazed connection. A distinction between different rake faces and flanks is not provided in this tool.